Patent Document 1 discloses a polishing pad comprising a polymer polymerized from polyurethane and a vinyl compound. Patent Document 2 discloses a process for producing a polishing pad, which comprises the steps of immersing a polymer molding in a solution containing a polymerizing monomer and causing a polymerization reaction of the monomer.
However, a conventional polishing pad was insufficient in in-plane uniformity of a polishing rate during polishing because of large variation in properties in or between pads. Also, low pad strength causes problems such as quick abrasion of the pad and a short pad lifetime during polishing.
Furthermore, since a polymerization reaction begins while a polymer molding is impregnated with a monomer and viscosity increases in the production of these polishing pads, there arises a problem that an impregnation rate to the polymer molding decreases and the time required for the production increases. In order to avoid an increase in viscosity, an impregnation temperature must be set to a low temperature and impregnation at a low temperature requires a long impregnation time. Furthermore, a drastic decrease in the impregnation rate caused by an increase in viscosity is prevented by adding an organic solvent to a polymerizing monomer to prepare a solution. Therefore, the step of removing a waste organic solvent after completion of the polymerization was required.    [Patent Document 1] International Publication No. WO00/12262    [Patent Document 2] Japanese Unexamined Patent Publication (Kokai) No. 2000-218551